here's the dealio...
well first off - i recommend kingston class 4 - never had a problem
when you plug it into the computer, did you turn the camera on? you must turn it on and it will switch over to USB mode and then show up on the computer.
Is your camera dead dead now? How did it get like that in the first place? what did you do?
Try taking out the battery and putting it back in . when you plug it into the wall, does the light turn on as if it's charging?
If it's dead dead then submit a support case to gopro (www.gopro.com/support) and they will take care of you